clef

clef,(
French: “key”) in musical notation, symbol placed at the beginning of the staff, determining the pitch of a particular line and thus setting a reference for, or giving a “key” to, all notes of the staff. Three clef symbols are used today: the treble, bass, and C clefs, stylized forms of the letters G, F, and C, respectively.

Music for instruments and voices is written in the clef corresponding most closely to the range of their parts. The treble, or G, clef fixes the position of the G above middle C. In modern notation this is invariably the second line from the bottom of the staff: